Alternating current (AC) power supplies are generally classified into an SMPS system and a linear power supply system, of which the SMPS method is mainly used in most applications including consumer electronics, computer, and communication equipment
The rapid surge of demand for LED lighting has encouraged extensive development efforts toward LED lighting using an SMPS device.
The LED has a low driving voltage (Vf) which requires an increase of the drive current (If) to manufacture a high-output lighting equipment that will also be desirable with less flickering. Therefore, such an LED lighting equipment needs to have a high-capacitance capacitor at its output end.
However, the LED illuminates with about 15% of the power consumption and turns approximately 85% of remaining power to thermal energy, resulting in a sudden rise in ambient temperature.
Moreover, there is a size restriction to a smaller lighting equipment that needs to accommodate mounting of all the LEDs and the power supply circuit such as the SMPS, which generate heat leading to malfunctions thereof, as realized by recent product recalls in the United States and Japan due to resultant fires, electric shocks, and the like.
In addition, such heat radiation is responsible for reducing the SMPS lifespan as short as less than 20,000 hours against the LED lifetime of approximately 35,000 hours. According to a U.S. Department of Energy: DOE's 2012 report, approximately ¼ of the LED lighting equipment sold in the US breaks within 1,000 hours of operation time, and the majority of these failures are known to occur in electrolytic capacitors of the SMPS.
There have been attempts to resolve the above-mentioned faults by designing SMPS and LED to be isolated from each other or using a solid capacitor instead of the electrolytic capacitor and the like. However, such known solutions are intolerant of some difficult conditions, failing to achieve an appreciable improvement in the SMPS lifespan and are too costly to realize a commercialization.